<!DOCTYPE html>
<html>
<head>
	<title>设计模式</title>
	<script src="js/jquery-3.5.1/jquery-3.5.1.min.js"></script>
</head>
<body>
	
</body>
</html>
	
<script>
	var createSingle = function(fn){
		var result = null;
		return function(){
			return result || (result = fn.apply(this, arguments));
		}
	}
</script>


